Heat stress impacts cattle the most when they are exposed to hot and humid weather for a period of time.

With warm weather in the forecast, cattle producers need to have a plan to lessen heat stress in their animals.

Heat stress has the greatest impacts when cattle are exposed to a combination of elevated temperatures and humidity for a period of time, according to North Dakota State University Extension Service animal experts. Hot and humid conditions during the day can stress cattle, but cooler temperatures at night will provide relief for cattle and equip them to face warmer daytime temperatures.

“If forecast models are correct, daytime highs in the upper Great Plains may be in the 80s to 90s, but the nighttime temperatures in the mid-60s should allow for nighttime cooling,” Extension livestock stewardship specialist and veterinarian Gerald Stokka says. “However, as we progress into the hottest part of the summer, a quick review of steps producers can take to manage and monitor conditions for heat stress is in order.”

Being proactive is the best way to deal with heat stress in cattle, he adds. To anticipate when heat stress conditions will be developing, actively monitor temperature and humidity forecasts.

“Once cattle are in a severe state of heat stress, you may be too late to help them,” Extension beef cattle specialist Carl Dahlen cautions. “Having a solid management plan in place to address heat stress could pay big dividends in the form of maintained animal performance during periods of heat and in avoiding death losses in severe cases.”

Heat stress occurs when cattle are not able to dissipate heat.

Mammals have involuntary methods of regulating their internal body temperature, including shivering and sweating to maintain “homeostasis,” or a constant, stable environment, Stokka says. Signs that animals are trying to maintain homeostasis include an increasing respiration rate, increased heart rate and increased panting. While animals are using extra energy, their feed intake declines.

Dahlen and Stokka recommend producers take the following steps to protect cattle from heat stress:

  • Identify animals that are most susceptible to heat stress. They include feedlot animals closest to the market endpoint, very young and very old animals, and those with dark hides.
  • Develop an action plan to deal with heat stress.
  • Know when to intervene. A combination of factors, including temperature and humidity, drives heat stress.

An action plan should include the following:

  • Give each animal access to at least 2 inches of linear water trough space in a pen. This means that in a pen with 200 animals, you need to have 400 inches of linear water space. If your cattle have access to only small water troughs, add temporary space for additional water access during the summer.
  • Evaluate your water supply lines and ensure you have sufficient water pressure and flow capacity to keep troughs full during times of peak water consumption.
  • Move the animals’ feeding time to late afternoon or evening. This will allow rumen fermentation to take place during the cooler night temperatures, and it will increase the cattle’s lung capacity during the hotter daytime temperatures.
  • If feeding once daily, consider moving feed delivery until the afternoon. If feeding multiple times daily, consider feeding a small meal in the morning and a larger portion of the diet later in the afternoon. Decrease the amount of feed offerings during and for several days after heat stress.
  • Provide adequate air movement. Remove unessential wind barriers (portable wind panels, equipment, weeds and other objects) to promote better air movement. Having mounds in pens gives cattle more elevation and possibly access to a microclimate with more wind.
  • Cool the ground and the cattle gradually. Sprinklers cool the ground cattle are lying on as much as they cool the cattle. Set up sprinklers well in advance of anticipated heat stress because cattle take time to adapt to changes. Use the sprinklers during mildly hot days so cattle become accustomed to the sights, sounds and the cooling effects of the sprinklers. An alternative to sprinklers is running a hose into pens to wet the ground where cattle will be lying. Run the sprinklers or wet the ground before the day’s peak temperatures.
  • Be aware of the droplet size of water coming from the sprinklers. The goal is to have large droplets of water. A fine mist likely will make the pens even more humid and contribute to greater heat stress.
  • Provide shade if possible.
  • Add light-colored bedding (straw or corn stalks) to reduce the temperature of the ground on which cattle are lying. Apply bedding to the tops of mounds and other areas likely to have wind. Also, wet the bedding before or shortly after putting it out.
  • Control flies as much as possible because hot cattle tend to bunch together and flies will add to the stress of hot days.
  • Do not work cattle during temperature extremes. If working cattle is absolutely necessary, keep working time as short as possible, use calm-animal-handling techniques to minimize stress related to handling, and consider running smaller groups through the facility or into holding pens. Provide sufficient water in holding pens. Get started as early in the morning as daylight will allow. Do not work in the evening after a heat-stress day; cattle need this time to recover. Reconsider the necessity of working cattle during these periods; postpone or cancel some working events.
  • Pay attention to long- and short-term weather forecasts and have a copy of the temperature humidity index chart readily available. Determine the potential risk threshold and be prepared, even if the risk is several index units away.

The U.S. Department of Agriculture has a heat stress forecast tool at http://www.ars.usda.gov/npa/marc/heatstress.

“Also, remember that interventions causing animals distress or to cool extremely rapidly could have disastrous consequences,” Stokka says.